An issue was discovered in Mattermost Server before 5.21.0. mmctl allows directory traversal via HTTP, aka MMSA-2020-0014.

An issue was discovered in Mattermost Mobile Apps before 1.29.0. The iOS app allowed Single Sign-On cookies and Local Storage to remain after a logout, aka MMSA-2020-0013.

An issue was discovered in Mattermost Server before 5.22.0. The markdown renderer allows attackers to cause a denial of service (client-side), aka MMSA-2020-0017.

An issue was discovered in Mattermost Mobile Apps before 1.30.0. Authorization tokens can sometimes be disclosed to third-party servers, aka MMSA-2020-0018.

An issue was discovered in Mattermost Server before 5.23.0. Automatic direct message replies allow attackers to cause a denial of service (infinite loop), aka MMSA-2020-0020.

An issue was discovered in Mattermost Server before 5.23.0. Large webhook requests allow attackers to cause a denial of service (infinite loop), aka MMSA-2020-0021.

An issue was discovered in Mattermost Mobile Apps before 1.31.2 on iOS. Unintended third-party servers could sometimes obtain authorization tokens, aka MMSA-2020-0022.

An issue was discovered in Mattermost Server before 5.7. It allows a bypass of e-mail address discovery restrictions.

An issue was discovered in Mattermost Server before 5.7, 5.6.3, 5.5.2, and 4.10.5. It mishandles permissions for user-access token creation.

An issue was discovered in Mattermost Server before 5.7, 5.6.3, 5.5.2, and 4.10.5. It allows attackers to cause a denial of service (memory consumption) via an outgoing webhook or a slash command integration.

An issue was discovered in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6. It does not honor flags API permissions when deciding whether a user can receive intra-team posts.

An issue was discovered in Mattermost Server before 5.8.0. The first user is sometimes inadvertently a system admin.

An issue was discovered in Mattermost Server before 5.8.0. It does not always generate a robots.txt file.

An issue was discovered in Mattermost Server before 5.8.0. It allows attackers to partially attach a file to more than one post.

An issue was discovered in Mattermost Server before 5.8.0, when Town Square is set to Read-Only. Users can pin or unpin a post.

An issue was discovered in Mattermost Server before 5.8.0. It does not honor the domain requirement when processing a join request for an open team.

An issue was discovered in Mattermost Server before 5.8.0. It mishandles brute-force attacks against MFA.

An issue was discovered in Mattermost Server before 5.8.0, 5.7.2, 5.6.5, and 4.10.7. It allows attackers to cause a denial of service (memory consumption) via OpenGraph.

An issue was discovered in Mattermost Server before 5.8.0, 5.7.2, 5.6.5, and 4.10.7. Changes to e-mail addresses do not require credential re-entry.

An issue was discovered in Mattermost Server before 5.9.0, 5.8.1, 5.7.3, and 4.10.8. Changes, within the application, to e-mail addresses are mishandled.